private async Task <bool> VerifyInstruction(Instruction instruction, ICollection <Transaction> siblings)
        {
            if (siblings.Any(x => x.Instructions.Any(y => y.InstructionId.SequenceEqual(instruction.InstructionId))))
            {
                return(false);
            }

            if (!_signatureService.VerifyInstruction(instruction))
            {
                return(false);
            }

            return(!await _instructionRepository.HaveInstruction(instruction.InstructionId));
        }